Effect of guidewire on contribution of loss due to momentum change and viscous loss to the translesional pressure drop across coronary artery stenosis: An analytical approach

<p>Abstract</p> <p>Background</p> <p>Guidewire (GW) size and stenosis dimensions are the two major factors affecting the translesional pressure drop. Studying the combined effect of these parameters on the mean pressure drop (Δ<it>p</it>) across the stenosis is of high practical importance.</p> <p>Methods</p> <p>In this study, time averaged mass and momentum conservation equations are solved analytically to obtain pressure drop-flow, Δ<it>p</it>-<it>Q</it>, curves for three different percentage area blockages corresponding to moderate (64%), intermediate (80%), and severe (90%) stenoses. Stenosis is considered to be axisymmetric consisting of three different sections namely converging, throat, and diverging regions. Analytical expressions for pressure drop are obtained for each of these regions separately. Using this approach, effects of lesion length and GW insertion on the mean translesional pressure drop and its component (loss due to momentum change and viscous loss) are analyzed.</p> <p>Results and Conclusion</p> <p>It is observed that for a given percent area stenosis (AS), increase in the throat length only increases the viscous loss. However, increase in the severity of stenosis and GW insertion increase both loss due to momentum change and viscous loss. GW insertion has greater contribution to the rise in viscous loss (increase by 2.14 and 2.72 times for 64% and 90% AS, respectively) than loss due to momentum change (1.34% increase for 64% AS and 25% decrease for 90% AS). It also alters the hyperemic pressure drop in moderate (48% increase) to intermediate (30% increase) stenoses significantly. However, in severe stenoses GW insertion has a negligible effect (0.5% increase) on hyperemic translesional pressure drop. It is also observed that pressure drop in a severe stenosis is less sensitive to lesion length variation (4% and 14% increase in Δ<it>p </it>for without and with GW, respectively) as compared to intermediate (10% and 30% increase in Δ<it>p </it>for without and with GW, respectively) and moderate stenoses (22% and 48% increase in Δ<it>p </it>for without and with GW, respectively). Based on the contribution of pressure drop components to the total translesional pressure drop, it is found that viscous losses are dominant in moderate stenoses, while in severe stenoses losses due to momentum changes are significant. It is also shown that this simple analytical solution can provide valuable information regarding interpretation of coronary diagnostic parameters such as fractional flow reserve (FFR).</p

Machine Learning Framework to Identify Individuals at Risk of Rapid Progression of Coronary Atherosclerosis: From the PARADIGM Registry.

Background Rapid coronary plaque progression (RPP) is associated with incident cardiovascular events. To date, no method exists for the identification of individuals at risk of RPP at a single point in time. This study integrated coronary computed tomography angiography-determined qualitative and quantitative plaque features within a machine learning (ML) framework to determine its performance for predicting RPP. Methods and Results Qualitative and quantitative coronary computed tomography angiography plaque characterization was performed in 1083 patients who underwent serial coronary computed tomography angiography from the PARADIGM (Progression of Atherosclerotic Plaque Determined by Computed Tomographic Angiography Imaging) registry. RPP was defined as an annual progression of percentage atheroma volume ≥1.0%. We employed the following ML models: model 1, clinical variables; model 2, model 1 plus qualitative plaque features; model 3, model 2 plus quantitative plaque features. ML models were compared with the atherosclerotic cardiovascular disease risk score, Duke coronary artery disease score, and a logistic regression statistical model. 224 patients (21%) were identified as RPP. Feature selection in ML identifies that quantitative computed tomography variables were higher-ranking features, followed by qualitative computed tomography variables and clinical/laboratory variables. ML model 3 exhibited the highest discriminatory performance to identify individuals who would experience RPP when compared with atherosclerotic cardiovascular disease risk score, the other ML models, and the statistical model (area under the receiver operating characteristic curve in ML model 3, 0.83 [95% CI 0.78-0.89], versus atherosclerotic cardiovascular disease risk score, 0.60 [0.52-0.67]; Duke coronary artery disease score, 0.74 [0.68-0.79]; ML model 1, 0.62 [0.55-0.69]; ML model 2, 0.73 [0.67-0.80]; all P&lt;0.001; statistical model, 0.81 [0.75-0.87], P=0.128). Conclusions Based on a ML framework, quantitative atherosclerosis characterization has been shown to be the most important feature when compared with clinical, laboratory, and qualitative measures in identifying patients at risk of RPP

INFLUENCE OF HEART RATE AND EPICARDIAL STENOSIS SEVERITY ON CARDIAC CONTRACTILITY UNDER CONCOMITANT MICROVASCULAR DISEASE IN A PORCINE MODEL SBC2011-53512

ABSTRACT Invasive guide wire methods to assess functional severity of coronary stenosis are affected by dynamic variables like heart rate (HR), contractility, epicardial stenosis (AS) and blood pressure. The interdependence of these factors is also influenced by the presence of concomitant microvascular disease (CMVD). The purpose of this study is to assess the variation in contractility under varying HR and AS in the presence of CMVD. In vivo experiments were performed on seven Yorkshire pigs. It was found that, in the presence of concomitant microvascular disease (CMVD), for lower AS (&lt;50%) contractility increases for HR&lt;120 bpm while it marginally decreases for HR&gt;120 bpm. However, for higher AS (&gt;50%), contractility decreases for both HR&lt;120 bpm and HR&gt;120 bpm. INTRODUCTON Quantification of the functional significance of epicardial coronary stenosis is important to diagnose heart diseases. In addition, in most clinical cases an obstruction in the coronary microvasculature might also be present under concomitant microvasculature disease, (CMVD) and can affect the clinical diagnostic measurements. Thus, quantification of the combined effect of epicardial and microvascular dysfunction is very much needed. The recent development of Dopplertipped guide wires and pressure monitoring guide wires has facilitated the invasive measurements of coronary flow velocity and distal pressure, thus reviving interest in the invasive physiological assessment of coronary artery disease. However, invasive measurements take place in a dynamic environment involving fluctuating hemodynamic variables like the blood pressure, contractility (CY) of the heart, epicardial stenosis (AS) and the heart rate (HR). To avoid any ambiguity in the evaluation of coronary circulation, the interdependence of these variables need to be clearly delineated. Accordingly, the goal of the present study was to evaluate the influence of changes in HR and AS on the left ventricular CY, measured as the maximum value of the derivative of left ventricular pressure (dp/dt) max METHODS The animal protocol for this study was approved by the University of Cincinnati IACUC and the Cincinnati Children&apos;s Hospital Medical Center. Seven Yorkshire swine (mean wt. 50 ± 3 kg) were premedicated with intramuscular xylazine (2 mg/kg), telazol (7 mg/kg), and atropine (0.05 mg/kg) and anesthesia was maintained with 2% isoflurane and supplemental oxygen. Three surgical accesses were made: 1) the jugular vein access was used to vary the HR by inserting pacing leads (Medtronics Inc., MN) into the right atrium; 2) second access through the carotid artery was used to advance a Millar © solid-tip catheter into the left ventricle, to measure the left ventricular pressure (recorded using Sonometrics system, Ontario, CN); 3) the third access, through the femoral artery, was used to engage a 7-F guiding catheter at the coronary ostium. Access to the left anterior descending (LAD) was achieved using a 0.014&quot; guidewire under fluoroscopy guidance. The lumen crosssectional area was measured using an intravascular ultrasound (IVUS, 2.5-F, 40-MHz) catheter. A 0.014&quot; Combo wire (Volcano Corp., CA) was inserted distal to the balloon to measure pressure and velocity distal to lesion. Based on the artery size, an appropriate Voyager angioplasty balloon of rapid exchange type (Guidant Inc., IN) was introduced over the Doppler flow wire. The balloon was inflated to different diameters to create intraluminal epicardial stenosis of varying severity. Polystyrene microspheres of 90µm (Polysciences Inc., NY) were injected to creat

Evaluation of lesion flow coefficient for the detection of coronary artery disease in patient groups from two academic medical centers

In this study, lesion flow coefficient (LFC: ratio of % area stenosis [%AS] to the square root of the ratio of the pressure drop across the stenosis to the dynamic pressure in the throat region), that combines both the anatomical (%AS) and functional measurements (pressure and flow), was assessed for application in a clinical setting. Pressure, flow, and anatomical values were obtained from patients in 251 vessels from two different centers. Fractional flow reserve (FFR), Coronary flow reserve (CFR), hyperemic stenosis resistance index (HSR) and hyperemic microvascular index (HMR) were calculated. Anatomical data was corrected for the presence of guidewire and the LFC values were calculated. LFC was correlated with FFR, CFR, HSR, HMR, individually and in combination with %AS. The p <0.05 was used for statistical significance. LFC correlated significantly when the FFR (pressure-based), CFR (flow-based), and anatomical measure %AS were combined (r=0.64; p <0.05). Similarly, LFC correlated significantly when HSR, HMR, and %AS were combined (r=0.72; p <0.05). LFC was able to significantly (p <0.05) distinguish between the two concordant and the two discordant groups of FFR and CFR, corresponding to the clinically used cut-off values (FFR=0.80 and CFR=2.0). The LFC could also significantly (p <0.05) distinguish between the normal and abnormal microvasculature conditions in the presence of non-significant epicardial stenosis, while the comparison was borderline significant (p=0.09) in the presence of significant stenosis. LFC, a parameter that combines both the anatomical and functional end-points, has the potential for application in a clinical setting for CAD evaluatio

Machine learning in cardiac CT:Basic concepts and contemporary data

Propelled by the synergy of the groundbreaking advancements in the ability to analyze high-dimensional datasets and the increasing availability of imaging and clinical data, machine learning (ML) is poised to transform the practice of cardiovascular medicine. Owing to the growing body of literature validating both the diagnostic performance as well as the prognostic implications of anatomic and physiologic findings, coronary computed tomography angiography (CCTA) is now a well-established non-invasive modality for the assessment of cardiovascular disease. ML has been increasingly utilized to optimize performance as well as extract data from CCTA as well as non-contrast enhanced cardiac CT scans. The purpose of this review is to describe the contemporary state of ML based algorithms applied to cardiac CT, as well as to provide clinicians with an understanding of its benefits and associated limitations

Association study of 25 type 2 diabetes related Loci with measures of obesity in Indian sib pairs.

Obesity is an established risk factor for type 2 diabetes (T2D) and they are metabolically related through the mechanism of insulin resistance. In order to explore how common genetic variants associated with T2D correlate with body mass index (BMI), we examined the influence of 25 T2D associated loci on obesity risk. We used 5056 individuals (2528 sib-pairs) recruited in Indian Migration Study and conducted within sib-pair analysis for six obesity phenotypes. We found associations of variants in CXCR4 (rs932206) and HHEX (rs5015480) with higher body mass index (BMI) (β=0.13, p=0.001) and (β=0.09, p=0.002), respectively and weight (β=0.13, p=0.001) and (β=0.09, p=0.001), respectively. CXCR4 variant was also strongly associated with body fat (β=0.10, p=0.0004). In addition, we demonstrated associations of CXCR4 and HHEX with overweight/obesity (OR=1.6, p=0.003) and (OR=1.4, p=0.002), respectively, in 1333 sib-pairs (2666 individuals). We observed marginal evidence of associations between variants at six loci (TCF7L2, NGN3, FOXA2, LOC646279, FLJ39370 and THADA) and waist hip ratio (WHR), BMI and/or overweight which needs to be validated in larger set of samples. All the above findings were independent of daily energy consumption and physical activity level. The risk score estimates based on eight significant loci (including nominal associations) showed associations with WHR and body fat which were independent of BMI. In summary, we establish the role of T2D associated loci in influencing the measures of obesity in Indian population, suggesting common underlying pathophysiology across populations